ITPEC IP April 2023 Question 28
ITPEC IP April 2023 — Question 28 of 100
Selection is the relational operation that keeps only rows satisfying a condition, here Price ≥ 100 yen. Applied to the Product table, it returns the Scissors, Notebook, and Ruler records while preserving their columns. In SQL, this corresponds to filtering with a WHERE condition.
Answer (c)
Why not others:
- (a) Join combines related rows from two tables
- (b) Projection chooses particular columns rather than filtering rows
- (d) Union combines compatible rows from two result sets and removes duplicates under set semantics
Key rule: Selection filters rows; projection filters columns; join connects tables; union combines compatible result sets.
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